CC_NEWRENO(4)          FreeBSD Kernel Interfaces Manual          CC_NEWRENO(4)

NAME
     cc_newreno - NewReno Congestion Control Algorithm

SYNOPSIS
     #include <netinet/cc/cc_newreno.h>

DESCRIPTION
     The NewReno congestion control algorithm is the default for TCP.  Details
     about the algorithm can be found in RFC5681.

Socket Options
     The cc_newreno module supports a number of socket options under
     TCP_CCALGOOPT (refer to tcp(4) and mod_cc(9) for details) which can be
     set with setsockopt(2) and tested with getsockopt(2).  The cc_newreno
     socket options use this structure defined in
     <sys/netinet/cc/cc_newreno.h>:

     struct cc_newreno_opts {
             int name;
             uint32_t val;
     }

     CC_NEWRENO_BETA          Multiplicative window decrease factor, specified
                              as a percentage, applied to the congestion
                              window in response to a congestion signal per:
                              cwnd = (cwnd * CC_NEWRENO_BETA) / 100.  Default
                              is 50.

     CC_NEWRENO_BETA_ECN      Multiplicative window decrease factor, specified
                              as a percentage, applied to the congestion
                              window in response to an ECN congestion signal
                              when net.inet.tcp.cc.abe=1 per: cwnd = (cwnd *
                              CC_NEWRENO_BETA_ECN) / 100.  Default is 80.

MIB Variables
     The algorithm exposes these variables in the net.inet.tcp.cc.newreno
     branch of the sysctl(3) MIB:

     beta          Multiplicative window decrease factor, specified as a
                   percentage, applied to the congestion window in response to
                   a congestion signal per: cwnd = (cwnd * beta) / 100.
                   Default is 50.

     beta_ecn      Multiplicative window decrease factor, specified as a
                   percentage, applied to the congestion window in response to
                   an ECN congestion signal when net.inet.tcp.cc.abe=1 per:
                   cwnd = (cwnd * beta_ecn) / 100.  Default is 80.

SEE ALSO
     cc_cdg(4), cc_chd(4), cc_cubic(4), cc_dctcp(4), cc_hd(4), cc_htcp(4),
     cc_vegas(4), mod_cc(4), tcp(4), mod_cc(9)

     Mark Allman, Vern Paxson, and Ethan Blanton, TCP Congestion Control, RFC
     5681.

     Naeem Khademi, Michael Welzl, Grenville Armitage, and Gorry Fairhurst,
     TCP Alternative Backoff with ECN (ABE), RFC 8511.

ACKNOWLEDGEMENTS
     Development and testing of this software were made possible in part by
     grants from the FreeBSD Foundation and Cisco University Research Program
     Fund at Community Foundation Silicon Valley.

HISTORY
     The cc_newreno congestion control algorithm first appeared in its modular
     form in FreeBSD 9.0.

     The module was first released in 2007 by James Healy and Lawrence Stewart
     whilst working on the NewTCP research project at Swinburne University of
     Technology's Centre for Advanced Internet Architectures, Melbourne,
     Australia, which was made possible in part by a grant from the Cisco
     University Research Program Fund at Community Foundation Silicon Valley.
     More details are available at:

     http://caia.swin.edu.au/urp/newtcp/

AUTHORS
     The cc_newreno congestion control module was written by James Healy
     <jimmy@deefa.com>, Lawrence Stewart <lstewart@FreeBSD.org> and David
     Hayes <david.hayes@ieee.org>.

     Support for TCP ABE was added by Tom Jones <tj@enoti.me>.

     This manual page was written by Lawrence Stewart <lstewart@FreeBSD.org>.

FreeBSD 13.1-RELEASE-p6          May 13, 2021          FreeBSD 13.1-RELEASE-p6